Research On Allelopathy Of Wedelia Chinensis

This article preliminarily studied the allelopathy of Chinese Wedelia. Chinese wedelia is a kind of perennial herbaceous plant with creepy body. It belongs to compositae wedelia and commonly grows in a low bank of earth between fields, such as the edge of road, raceway, hill channel, humid grassplot and farmland. It seldom invades into farmland to endanger crops. It scatters broadly in south China and often grows by connecting into a slice, there are little other kinds of weed growing in its community. Chinese wedelia has exuberant growth competition, and this dominance relates to its allelopathy. This article started with the allelopathy, and then studied the influence of Chinese wedelia water, ethanol, Methylene chloride extracts to various plant seeds germination, seedling growth and the toxicity to Scenedesmus obliquus. Its aim is to open out whether Chinese wedelia has the allelopathy to other plants, and to offer a experiment basis for the exploitation of new botanical pesticide.This experimentation result indicated that each of Chinese wedelia water extract concentrations had tarnal notable restraint to Amaranthus retroflexus seed germination, and had notable reatraint to Echinoloa crusgalli seed germination.For radish, rice, cole, mustard, EcIipta prostrata L.and Setaria viridis (L.)Beauv,there was at least one Chinese wedelia water extract concentration which had no notable influence on their seed germination. because of the restraint to plant, there had direct ratio between seed germination ratio and the extract concentration, showed more or less concentration-dose connection, so concentrations that had no notable influence to plant germination were low extract dose, the high dose had evident restraint to seed germination. The 0.075 mL Chinese Wedelia extract dose had no notable effect to radish, cole, mustard seed germination, 0.15 mL and 0.075 mL dose had the same influence to Setaria viridis (L.)Beauv..As for rice and EcIipta prostrata L., Chinese Wedelia water extract, only 0.50 mL dose had notable effect to their seed germination.Each of the Chinese Wedelia ethanol extract dose had notable restraint to radish, cole, mustard, Eclipta prostrate L., Setaria viridis (L.)Beauv., Amaranthus retroflexus seed germination, some disposals achieved 1% tarnal notable level compared with blank, and showed concentration-dose connection that the restraint toned up along with the augmentation of the extract concentration. The restraint to Amaranthus retroflexus and Setaria viridis (L.)Beauv. was especially obvious: by the 0.50 mL and 0.30 mL dose processed, Amaranthus retroflexus seed germination ratio were all 0.0%, and it's 2.8% under treatment with 0.15 mL and 0.075 mL, and that blank comparison was 86.1%; At the condition of all doses, Setaria viridis (L.)Beauv. seed germination ratio was 0.0%, 2.8%, 8.3%, 11.1% respectively, and that the blank comparison was 77.8%; The result showed that each Chinese Wedelia ethanol extract dose had no notable influence on seed germination of Echinochloa crusgalli (L.) Beauv and rice, but still had more or less restraint.Each of Chinese Wedelia methylene chloride extract dose had notable restraint to seed germination of cole, Amaranthus retroflexus, EcIipta prostrata L., Setaria viridis (L.)Beauv, some dose achieved 1% tarnal notable level compared with blank, and that between the concentration of extract and restraint there had a linear connection: the restraint strengthen when extract concentration augment. Processed with 0.50 mL dose, Chinese Wedelia methylene chloride extract had notable restraint to germination of Echinochloa crusgalli (L.) Beauv, between the other low doses and the comparison it had no notable difference. As for mustard, all the Chinese Wedelia methylene chloride extract doses had notable restraint to its germination except 0.075 mL dose; For radish and rice, between all disposals and comparison there had no notable defference, but still had more or less restraint.Chinese Wedelia water, methylene chloride, ethanol extract all had allelopathy(mostly restraint) to seedling root and sprout growth and increase of fresh weight of the eight examined plants, and that showed definite concentration-dose connection, the restraint to root was more intense than that to sprout; When in low dose, Chinese Wedelia water extract sometimes accelerated the development of seedling(root, sprout, fresh weight) of radish, rice and Echinochloa crusgalli (L.) Beauv. All of Chinese Wedelia methylene chloride and ethanol extract doses had restraint to development(root, sprout, fresh weight) of tested plants, and the restraint to cole, EcIipta prostrata L., Setaria viridis (L.)Beauv. was especially evident, and the ratio were mostly more than 90.0%, even up to 100.0%.After irrigated with Chinese Wedelia water, methylent chloride and ethanol extract, the tested 8 potted plants all showed yellow leaf, death of individual plant, plants were growing weakened, both height and fresh weight decreased notablely compared with blank.The allelopathy of Chinese Wedelia water, methylene chloride, ethanol extract to Scenedesmus obliquus were obvious, compared with blank; the algae cells of disposed Scenedesmus obliquus greatly reduced, and showed concentration-dose connection, that algae cells reduced along with the augmentation of the extract concentration. The LD50 of each extract to Scenedesmus obliquus was downtrend along with time extension; The LD50 of ethanol extract to Scenedesmus obliquus was commonly low compared with the other two extracts. The value of LD50 were 0.002%, 0.052% and 0.001% respectively at 48 h, 72 h and 96 h.